3 Answers
3

After some more research, it reminds me that finder's spotlight had boolean UI since OS X 10.5. You can filter for "not a folder" for All My Files experience, or with a little bit more filter for "all files".

I can verify that this works on Yosemite. You may need to hold down the ALT/Option key to make the little plus sign on the right side change to three dots. Click the three dots, then the menu with "None of the following are true" will appear.
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NateFeb 4 at 17:02

That's not what I meant. This option is only for the default searched location when you enter/trigger spotlight in finder. You can also change this while searching with finder's spotlight. The thing is, when you enter spotlight, there will be no result at all when you haven't type anything.
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DaveOct 2 '11 at 8:50